1. Field of the Invention
This invention relates to a vibration driven motor apparatus.
2. Related Background Art
As a prior-art vibration driven motor apparatus, there is one as shown, for example, in FIGS. 5 and 6 of the accompanying drawings.
In FIG. 5, the reference number 18 designates an elastic member formed of a metal material formed into an elliptical shape having two arcuate portions and two straight portions and having a piezo-electric element group 21 joined to the underside thereof. The elastic member 18 is supported on a substrate 22, for example, through a vibration insulating member 19 formed of felt. Guide shafts 23 are fixed to the widthwise opposite end portions of the substrate 22, and linear bearings 24 extend through these shafts, respectively. These linear bearings 24 are fixed to the opposite end portions of moving member 20 which is movable along the lengthwise direction of the shafts 23 indicated by arrow A. A leaf spring 25 is fixed to the underside of the moving member 20 correspondingly to the straight portion of the elastic member 18, and a friction plate 26 is fixed to the spring end portion of the leaf spring 25 as by a bolt, and is brought into pressure contact with the elastic member 18 by the spring force of the leaf spring 25.
According to such structure, the elastic member 18 generates a travelling wave upon application of an AC voltage to the piezo-electric element group 21, and even if it slides vertically and to left and right on the vibration insulating member, the moving member 20 is driven only in the direction of arrow A by the elastic member 18 because it is held between the bearings 24, and the moving member 20 effects rectilinear movement.
In the above-described example of the prior art, however, linear bearings are used as bearings, and where these bearings are linear ball bearings, there has been the problem that although bearing resistance is small, the apparatus is costly and is not free of the sliding sound of balls
Also, where the bearings are slide bearings, a reaction force which presses the friction plate 26 against the elastic member 18 is applied to the bearings, and this has led to the problem that bearing resistance becomes great.